1. Field of the Invention
The present invention relates to a method for measuring the surface temperature of a semiconductor wafer substrate, and also to a heat-treating apparatus.
2. Description of the Related Art
In an apparatus which manufactures a semiconductor device by heat-treating a semiconductor wafer substrate, the treated condition of the substrate is dependent greatly on the treating temperature. Therefore, how the treating temperature is controlled an important factor in determining the characteristics of a semiconductor device. It should be noted that the surface on the major side of the substrate (i.e., the surface on which a thin film or the like is to be formed) constitutes an important portion of the semiconductor device to be manufactured. Therefore, the temperature of that surface has to be measured accurately and controlled in an optimal manner in the manufacturing process of the semiconductor device. (The surface on the major side of the substrate will be hereinafter referred to as a "major surface"; likewise the surface on the opposite side of the substrate will be hereinafter referred to as a "minor surface".)
To measure the temperature of a substrate treated in a semiconductor device-manufacturing apparatus, one prior art method employs a contact type thermometer in which a thermocouple is incorporated. The thermometer is arranged on the platen on which the substrate is mounted. In this prior art method, the temperature of the platen can be measured, but the temperature of the major surface of the substrate cannot be accurately measured since there is a large temperature difference between the platen and the major surface of the substrate. If the thermocouple of the thermometer is arranged not on the platen but on the major surface of the substrate, the temperature of the major surface may be measured with accuracy. In this case, however, the thermocouple will become a physical obstacle to the formation of films on the major surface. It should be also noted that the thermocouple is slow in reacting to a temperature change.
Another prior art method employs a non-contact type radiation thermometer. This radiation thermometer measures the temperature of the substrate by detecting infrared rays of e.g about 5 .mu.m radiated from the substrate. In this method, it is necessary to know the emissivity of the substrate before the temperature measurement. However, if the emissivity of the substrate is unknown or if the emissivity varies in accordance with a change in the surface condition of the substrate (for example, the emissivity may be different before and after a film is formed on the surface of the substrate), it is difficult to accurately measure the temperature. In addition, since the radiation thermometer receives more infrared rays from the substrate bulk than from the film coated on the surface of the substrate, it is difficult to accurately measure the surface temperature itself.